Salvia nemorosa 'Caradonna'
This drought-tolerant perennial is noted for its vivid indigo flowers along deep purple-black stems, which gives it a bicolor appearance. It blooms in early summer and then sporadically if spent flowers are deadheaded. It forms an upright clump, with the flower spikes rising to 2 feet in height; its wrinkled, softly hairy leaves form a mound 1 foot high. Plants spread 1 or 2 feet wide. These are some of the showiest plants for containers and mixed borders. Butterflies love them.